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Structural Design Key Differences: Fixed vs. Movable Types
Fixed Insulated Steel Fire Windows
Fixed insulated steel fire windows are not fitted with opening-closing hardware with properly simplified frame sections. The wall thickness of frames and mullions is at least 1.2 mm, and 1.5 mm profiles are recommended for Class A fire-resistant products. Equipped with thermal insulation cavities, composite fire-resistant glass and double sealing, reinforced sealing structures are arranged at frame-wall joints. Complying with both integrity and insulation standards, it limits temperature rise on the unexposed surface to block high temperature, smoke and flame. Without openable gaps, it resists thermal deformation and corrosion, suitable for exterior observation windows and indoor partition daylighting parts for fixed fire separation.
Movable Insulated Steel Fire Windows
Movable insulated steel fire windows are fitted with self-closing devices, fire-resistant hinges and fire locks for normal opening and closing. The nominal wall thickness of main frame materials is no less than 1.2 mm, while standard sash frames have a minimum thickness of 1.0 mm; sashes wider than 1.8 m shall be thickened to 1.2 mm. Wider frame-sash overlapping surfaces and double-channel intumescent seals are adopted, with gaps strictly controlled within 3 mm. The windows meet both fire integrity and insulation requirements, automatically closing to block smoke and flames in fire conditions. Heat-resistant and anti-corrosive, they are widely used in stairwells, refuge rooms, equipment rooms and other areas requiring fire separation and observation openings for evacuation
Fire Resistance Classification & Assessment Criteria
Class A insulated steel fire windows must satisfy both fire resistance assessments: Integrity (E) and Insulation (I). The furnace temperature shall follow the standard temperature-time curve, reaching 925 °C at 60 minutes and 986 °C at 90 minutes. The evaluation thresholds are specified below
Integrity (E)
Throughout the entire fire resistance test, there shall be no continuous flame penetration or through gaps, the glass shall not detach, and the frame and sash shall not collapse or deform severely. A 6 mm test probe shall not penetrate any gap to a depth of 150 mm or more, and the cotton pad arranged on the unexposed side shall not be ignited at any time during testing.
Insulation (I)
In terms of fire insulation index requirements, the average temperature rise on the unexposed surface of the window shall not exceed 140℃, the peak temperature rise of any single measuring point shall be less than or equal to 180℃, and the heat flux passing through the window assembly shall be restricted to a maximum limit of 15kW per square meter.
Classification Specifications
A1.50 (Grade 1 Fire Resistance): Minimum 1.5 hours of integrity and insulation performance. Applied to refuge rooms, fire partition walls and atrium separation.
A1.00 (Grade 2 Fire Resistance): Minimum 1.0 hours of integrity and insulation performance. Applied to stairwell antechambers and fire separation for factory buildings.
Mandatory National Standard Parameters for Substrate Wall Thickness
1.Window frames and mullions (load-bearing components of fixed main frames) The national standard minimum mandatory wall thickness shall be no less than 1.2 mm. For Class A high fire resistance insulated types (meeting both integrity (E) and insulation (I) requirements with a 90-minute fire resistance rating), a thickness of 1.5 mm is recommended for construction projects. Application scenarios: Class A fire windows for exterior wall fixed observation windows, stairwells and refuge rooms. The increased thickness resists thermal deformation under high temperatures and prevents frame warpage, smoke leakage and flame penetration.
2.Movable sash frames (openable casement sashes) The mandatory minimum wall thickness for standard-sized sashes shall be no less than 1.0 mm. Oversized sash reinforcement requirement: any single sash with a width exceeding 1.8 m must be thickened to 1.2 mm. Rationale: Larger sashes suffer greater thermal deformation when exposed to fire. Insufficient wall thickness will cause excessive gaps between the sash frame and window frame (gaps shall be strictly controlled within 3 mm), impairing fire and smoke sealing performance.
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